The present invention relates to medical equipment, techniques and procedures, and more particularly, to the circulation and recovery of blood during and immediately following heart bypass surgery.
A persistent dilemma is faced thousands of times each day worldwide, of how to handle the volume of a patient's blood in the circuit of a cardiac pulmonary bypass system (heart-lung machine), after the surgical procedure has been completed and the patient is disconnected from the bypass system.
One option is to transfuse the volume in the cardiopulmonary bypass (CPB) circuit to the patient, in the manner of a blood transfusion, without compromising the integrity of the bypass system. It should be appreciated that the CPB circuit includes a crystalloid priming fluid which is necessary to initiate the pumping of the circuit. Therefore, transfusion of the content of the circuit would include transfusion of the priming solution which, by the end of the surgery, has been fully mixed with the patient's own blood. The hematocrit concentration is therefore low, i.e., approximately 18-23%. Although some such diluted blood can be transfused to the patient, a relatively large fraction of the volume of the CPB circuit cannot be transfused, because this volume is needed to maintain the integrity of the circuit in the event full bypass is to be resumed.
Alternatively, the content of the CPB circuit can be transferred to sterile blood bags, for a possible re-transfusion to the patient either in or out of the operating room. This option also suffers from the dilution of important blood components and the need to keep a large fraction of the diluted blood in the circuit to maintain circuit integrity.
Yet a third option, is to chase all the volume in the CPB circuit with a crystalloid solution to a so-called “cell saver”, where the fluid volume is separated into red blood cells and effluent. Although the red blood cells are saved, the effluent is deemed waste and therefore discarded, yet the effluent contains many desirable constituents of whole blood, such as plasma, platelets, clotting factors, albumin, etc.
Finally, the most straight-forward option is to seal or drain and discard the content of the CPB circuit. This is common in pediatric open heart cases, but benefits neither the patient nor anyone else, and presents a significant disposal problem to the perfusionist (i.e., the operator of the heart/lung machine), who must clean up and discard this wasted volume.
Because in the foregoing options, the patient cannot receive his own entire blood volume from the CPB circuit immediately following cardiac, thoracic, or vascular procedures, if the need for additional blood arises, the only available source is from previously stored blood bags. If the patient gave blood prior to surgery, which is rare, then the patient could receive so-called autologous blood. Most often, however, such additional blood or blood products would be provided from a dwindling blood bank supply, which originated from an allogeneic (unknown) donor. Transfusing such blood can arouse anxiety and create problems including hemolytic reactions, viral hepatitis-C, and potentially, blood viruses or AIDS, and the new onset of vCJD or Prion's disease (BSE). Human error can occur when mistakes are made by giving non-compatible or mislabelled blood products. There is also a new surgence of artificial blood substitutes or HBOC's, but these are limited to carrying only oxygen, have a short half-life and do not compare favorably to the miraculous abilities of the patient's own blood. Lastly, there is also a small population of patients that completely refuse any foreign blood or blood products of any kind, due for example, to religious beliefs.
Because of these reasons, the need exists to reduce allogeneic blood use and strive for “bloodless surgery” and the growing movement towards bloodless medicine.